Objects in R

2023 Bio R Workshop

An Intuitive Framework

One approach to get a partial yet quick understanding of a complex system of ideas is to have a simplified mental picture of it. This same approach is applied when we want to learn R as its learning is quite steep:

“The learning curve for R programming is steep due to its unique syntax and extensive set of commands, requiring most new learners to spend four to six weeks mastering it.” - Noble Desktop, (NYC’s Top Design & Coding School Since 1990)

A (over)simplified mental picture for beginners of R is to analogize working in R as cooking. Cooking essentially requires three things:

1. Ingredients – R objects a.k.a “data containers”
2. Cooking utensils/equipments – R functions
3. Recipe – R scripts or Markdown files

Figure 1: Mental picture when working with R

You can think of RStudio’s Console and Source Panes as the “chef’s” (you) cooking table.

Vectors

Probably the most fundamental object that act as “data container” (i.e. data structure) in R is called a vector (also called atomic vectors). Almost all other objects in R that are used by the common user is built up in terms of vectors. Any vector contains three properties:

1. Type - typeof(), what it is
2. Length - length(), how many elements it contains
3. Attributes - attributes(), additional arbitrary metadata

Creating vectors could be done in many ways. However, two of most basic ways depends on the length of the vector:

1. Length = 1. Directly run a single alphanumeric characters in the Console Pane.
2. Length > 1. Use the R combined command c().

Characters or Strings

"a"
"a,    b,c"
c("a","b","c")

typeof("a")
typeof("a,    b,c")
typeof(c("a","b","c"))

length("a")
length("a,    b,c")
length(c("a","b","c"))

Numbers

15L
1.0
1 + 2i

c(1L,2L,0L,-15L)
c(1.0,1,4,6,-56,1e-10,1e4)
c(1 + 2i,1,0 - 3i, 3i)

typeof(15L)
typeof(1.0)
typeof(1 + 2i)

typeof(c(1L,2L,0L,-15L))
typeof(c(1.0,1,4,6,-56,1e-10,1e4))
typeof(c(1 + 2i,1,0 - 3i, 3i))

length(15L)
length(1.0)
length(1 + 2i)

length(c(1L,2L,0L,-15L))
length(c(1.0,1,4,6,-56,1e-10,1e4))
length(c(1 + 2i,1,0 - 3i, 3i))

Logical or Boolean

T
F
TRUE
FALSE
c(T,FALSE)
c(T,T,T,T,F,FALSE,F,TRUE,T,FALSE,T)

typeof(c(T,FALSE))
length(c(T,FALSE))
attributes(c(T,FALSE))

Matrix

# Number of entries matches number of elements
matrix(c(1,2,3,4,5,6,7,8), nrow = 2, ncol = 4)
matrix(c(1,2,3,4,5,6,7,8), nrow = 2, ncol = 4, byrow = TRUE)

# Number of entries does not matche number of elements
# Resolved by recycling elements
matrix(c(1,2,3,4,5,6,7,8), nrow = 2, ncol = 10)
matrix(c(1,2,3,4,5,6,7,8), nrow = 2, ncol = 13, byrow = TRUE)

## Example of setting row and column names
matrix(data = c(1,2,3, 11,12,13), 
       nrow = 2, 
       ncol = 3, 
       byrow = TRUE,
       dimnames = list(c("row1", "row2"),
                       c("C.1", "C.2", "C.3")))